Skin Fat Helps Protect Against Infections, Study Finds

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Fat cells just under a person's skin may be the first responders
to invading bacteria, buying time until the white blood cells
arrive at a wound site, according to a new study.

The new findings suggest that the task of fighting infections is
not solely the responsibility of the immune system, the
researchers said. Moreover, fat cells may fight infections by
producing antimicrobial compounds, lab experiments in mice and
human fat cells showed.

"That was totally unexpected," study co-author Dr. Richard Gallo,
chief of dermatology at the University of California, San Diego
School of Medicine, said in a statement. "It was not known that
[fat cells] could produce antimicrobials, let alone that they
make almost as much" as immune system cells, he said.

When the skin is cut and exposed to pathogens, the immune
system sends specialized white blood cells, such as
neutrophils, to the wound site to kill the bacteria entering the
skin. But it takes time for these cells to reach the site of
injury.

In the experiments in mice, the researchers found that the layer
of fat under the skin at the site of an infection thickened, and
that the fat cells produced an antimicrobial compound called
cathelicidin. These findings suggest that these fat cells can
directly sense the staph bacteria and respond accordingly, the
researchers said.

In addition, mice that lacked healthy fat cells under the skin
suffered more frequent and severe infections with MRSA, according
to the study, published today (Jan. 2) in the
journal Science.

However, the findings don't mean that having too much fat in the
body will bring better protection against infections. In fact,
obesity or insulin resistance could result in having fat cells
that don't respond as they should, and may actually lower a
person's defense against infections, the researchers said. This
could explain the results of previous studies that found that
obese people may be at higher risk for skin infections, the
researchers said.